{"id":174,"date":"2026-07-08T08:58:38","date_gmt":"2026-07-08T08:58:38","guid":{"rendered":"https:\/\/industrialelectricmotor.net\/?p=174"},"modified":"2026-07-08T08:58:38","modified_gmt":"2026-07-08T08:58:38","slug":"what-is-a-worm-gear-reducer","status":"publish","type":"post","link":"https:\/\/industrialelectricmotor.net\/fi\/what-is-a-worm-gear-reducer\/","title":{"rendered":"What Is a Worm Gear Reducer"},"content":{"rendered":"
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Korea Ever-Power \u00b7 RV \/ NMRV Series \u00b7 Worm Gear Reducer Guide<\/span><\/p>\n

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What Is a Worm Gear Reducer?
\nRV Series Application Guide<\/span><\/h1>\n

A worm gear reducer converts the high speed, low torque output of a standard electric motor into low speed, high torque output through the action of a helical worm screw meshing with a worm wheel. The compact right-angle geometry, high single-stage gear ratio, and inherent self-locking capability at higher reduction ratios make the worm gear reducer the standard solution for conveyors, agitators, packaging machinery, and materials handling equipment across the 0.06 to 22 kW power range.<\/p>\n

Right-Angle Compact Design<\/span>
\n5:1 to 100:1 Single-Stage<\/span>
\nSelf-Locking at High Ratio<\/span>
\nAluminium Housing RV \/ NMRV<\/span>
\nIEC Flange Motor Mount<\/span><\/div>\n<\/div>\n<\/div>\n

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5:1\u2013100:1<\/div>\n
Single-stage ratio range<\/div>\n<\/div>\n
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7500:1<\/div>\n
Max two-stage ratio (dual gearbox)<\/div>\n<\/div>\n
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40\u201390%<\/div>\n
Efficiency range by ratio<\/div>\n<\/div>\n
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NMRV 025\u2013150<\/div>\n
Housing size range<\/div>\n<\/div>\n
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\u2264 22 kW<\/div>\n
NMRV input motor range<\/div>\n<\/div>\n<\/div>\n

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\"Worm<\/p>\n
Korea Ever-Power RV\/NMRV series worm gear reducer \u2014 the aluminium alloy housing provides a compact, lightweight right-angle drive unit that accepts IEC flange motor input directly, without an adapter or coupling. The worm wheel (bronze, visible on the output shaft axis) meshes with the hardened steel worm shaft driven by the motor input.<\/div>\n<\/div>\n

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Contents<\/div>\n
1. How a Worm Gear Reducer Works<\/a>
\n2. Self-Locking: When and Why It Applies<\/a>
\n3. RV and NMRV Series Overview<\/a>
\n4. Gear Ratio, Output Torque and Efficiency<\/a>
\n5. Thermal Rating and Duty Cycle<\/a>
\n6. Gearmotor Combinations<\/a>
\n7. Application Areas<\/a>
\n8. Frequently Asked Questions<\/a><\/div>\n<\/div>\n

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1. How a Worm Gear Reducer Works<\/h2>\n

A worm gear reducer consists of two main components: the worm (a helical screw shaft made from hardened alloy steel) and the worm wheel (a toothed wheel made from centrifugally cast bronze or ductile iron, mounted on the output shaft at 90 degrees to the worm shaft). The worm is directly connected to or integral with the input shaft driven by the motor. As the worm rotates, its helical threads engage with the teeth of the worm wheel, converting the high-speed rotary motion of the motor input into slow rotary motion of the output shaft at a right angle.<\/p>\n

The gear ratio of a worm gear reducer is determined by the number of starts on the worm and the number of teeth on the worm wheel. For a single-start worm meshing with a 60-tooth worm wheel, the gear ratio is 60:1 \u2014 the output shaft completes one revolution for every 60 revolutions of the input shaft. Standard single-stage ratios in the Korea Ever-Power RV\/NMRV series range from 5:1 to 100:1, covering output speeds from 29 rpm (100:1 at 2,900 rpm motor input) down to 290 rpm (5:1 at 1,450 rpm 4-pole motor input).<\/p>\n

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Worm Shaft Material<\/div>\n

20CrMnTi alloy steel, case-hardened to HRC 56\u201362, ground to Ra 0.4 \u03bcm finish. The hardened and ground worm shaft surface provides the wear resistance needed to maintain the precise tooth profile that determines backlash and efficiency over the service life of the reducer.<\/p>\n<\/div>\n

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Worm Wheel Material<\/div>\n

Centrifugally cast phosphor bronze (CuSn12) or ductile iron (for larger sizes). Bronze provides the conformability needed to develop a full contact pattern against the hardened steel worm under load, and the sacrificial wear behaviour that protects the harder worm from surface damage under misalignment or shock loading.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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2. Self-Locking: When and Why It Applies<\/h2>\n

Self-locking is the property by which a worm gear reducer cannot be back-driven \u2014 that is, torque applied to the output shaft cannot rotate the worm shaft. This occurs when the worm lead angle is less than the friction angle between the worm and worm wheel materials. For a single-thread worm at typical steel-on-bronze friction coefficients, self-locking occurs at gear ratios above approximately 20:1 to 30:1, depending on the specific worm geometry and lubricant viscosity.<\/p>\n

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When Self-Locking Is Useful<\/div>\n

Inclined conveyors: when the motor stops, the load on the inclined belt cannot roll back because the worm gear reducer holds the output shaft stationary under gravity loading. Lifting tables and vertical positioning stages: the platform remains at its set height when the motor is de-energised without a separate brake. Valve actuators: the valve remains at its set position without continuous power to an electromagnetic holding device. In all these applications, the self-locking worm gear reducer provides a passive, failsafe holding function at no additional cost or complexity.<\/p>\n<\/div>\n

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When Self-Locking Is Not Reliable<\/div>\n

Self-locking is not a certified safety mechanism and should never be relied upon for life-safety holding applications (man-riding hoists, safety gates, suspended loads over people). The self-locking property can be lost if lubricant viscosity drops under elevated temperature, if vibration is present in the system, or if the worm gear ratio is near the borderline (25:1 to 35:1 range). For safety-critical holding, a brake motor (Korea Ever-Power Y2EJ series) or a separate certified safety brake is required in addition to or instead of relying on worm gear self-locking.<\/p>\n<\/div>\n<\/div>\n

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Self-locking reference: NMRV and RV series worm gear reducers at ratios of 40:1 and above are reliably self-locking under normal operating conditions with standard gear oil viscosity. Ratios of 20:1 to 30:1 may or may not be self-locking depending on worm lead angle and operating temperature. Ratios below 15:1 are generally not self-locking.<\/p>\n<\/div>\n<\/div>\n

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3. RV and NMRV Series Overview<\/h2>\n
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The Korea Ever-Power RV and NMRV series are aluminium alloy worm gear reducers that accept a three-phase induction motor directly on the IEC B5 flange input. The \u201cNMR\u201d prefix denotes the refined aluminium alloy housing (compared to the original cast iron RV design); the \u201cV\u201d suffix indicates the integral IEC motor flange. The housing numbers (025, 030, 040, 050, 063, 075, 090, 110, 130, 150) correspond to the centre distance between the worm shaft and worm wheel shaft axes in millimetres.<\/p>\n

Korea Ever-Power NMRV units are available with hollow-shaft output (for direct shaft mounting without a separate coupling), solid output shaft in one or both directions, and a torque arm accessory for reaction force take-out. The full gearbox range with specifications is available in the worm gear reducer product section<\/a>.<\/p>\n<\/div>\n

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NMRV Series Size Range<\/div>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Size<\/th>\nMax Input (kW)<\/th>\nMax Output Torque<\/th>\n<\/tr>\n<\/thead>\n
NMRV 025<\/td>\n0.06<\/td>\n4 N\u00b7m<\/td>\n<\/tr>\n
NMRV 030<\/td>\n0.09<\/td>\n8 N\u00b7m<\/td>\n<\/tr>\n
NMRV 040<\/td>\n0.18<\/td>\n25 N\u00b7m<\/td>\n<\/tr>\n
NMRV 050<\/td>\n0.55<\/td>\n70 N\u00b7m<\/td>\n<\/tr>\n
NMRV 063<\/td>\n1.1<\/td>\n130 N\u00b7m<\/td>\n<\/tr>\n
NMRV 075<\/td>\n2.2<\/td>\n240 N\u00b7m<\/td>\n<\/tr>\n
NMRV 090<\/td>\n4.0<\/td>\n400 N\u00b7m<\/td>\n<\/tr>\n
NMRV 110<\/td>\n7.5<\/td>\n700 N\u00b7m<\/td>\n<\/tr>\n
NMRV 130<\/td>\n11<\/td>\n1,100 N\u00b7m<\/td>\n<\/tr>\n
NMRV 150<\/td>\n22<\/td>\n2,000 N\u00b7m<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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4. Gear Ratio, Output Torque and Efficiency<\/h2>\n

The output torque of a worm gear reducer is the motor shaft torque multiplied by the gear ratio and the gearbox efficiency, minus any mechanical losses. For a 4-pole motor at 1,450 rpm producing 4.0 kW (rated torque 26.4 N\u00b7m), connected to an NMRV 090 with a 40:1 ratio and 68 percent efficiency: output torque = 26.4 \u00d7 40 \u00d7 0.68 = 717 N\u00b7m at 36 rpm output. This is why even a modest 4 kW motor with a worm gear reducer can drive a heavily loaded slow conveyor or a large agitator \u2014 the torque multiplication at the gearbox output more than compensates for the efficiency loss at high ratios.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n
Ratio<\/th>\nOutput Speed (4P, 1450 rpm)<\/th>\nTypical Efficiency<\/th>\nSelf-Locking?<\/th>\nTypical Use<\/th>\n<\/tr>\n<\/thead>\n
5:1<\/td>\n290 rpm<\/td>\n88\u201392%<\/td>\nNo<\/td>\nHigh-speed conveyors, fans, light agitators<\/td>\n<\/tr>\n
10:1<\/td>\n145 rpm<\/td>\n82\u201387%<\/td>\nNo<\/td>\nMedium-speed conveyors, packaging drives<\/td>\n<\/tr>\n
20:1<\/td>\n72 rpm<\/td>\n75\u201382%<\/td>\nBorderline<\/td>\nSlow conveyors, agitators, winding machines<\/td>\n<\/tr>\n
40:1<\/td>\n36 rpm<\/td>\n65\u201375%<\/td>\nYes<\/td>\nInclined conveyors, lifting tables, valve drives<\/td>\n<\/tr>\n
60:1<\/td>\n24 rpm<\/td>\n55\u201365%<\/td>\nYes<\/td>\nSlow dosing, stirrers, barrier gate drives<\/td>\n<\/tr>\n
100:1<\/td>\n14.5 rpm<\/td>\n40\u201355%<\/td>\nYes<\/td>\nVery slow drives: solar trackers, pot stirrers, precision positioners<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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Efficiency note: worm gear efficiency decreases significantly at high ratios due to the sliding contact between worm and worm wheel. At 100:1 ratio, 45 to 60 percent of the input power is converted to heat in the gearbox. For continuous duty applications at high ratios (above 60:1), verify the gearbox thermal rating is not exceeded \u2014 the gearbox may need to be sized one step larger than the required torque to stay within the thermal limit at the operating cycle.<\/p>\n<\/div>\n<\/div>\n

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5. Thermal Rating and Duty Cycle<\/h2>\n

Because worm gear reducers generate significant heat through friction losses (especially at ratios above 30:1), the gearbox housing temperature during continuous operation is an important design constraint. Korea Ever-Power NMRV series reducers are thermal-rated for a maximum housing temperature of 80\u00b0C at 40\u00b0C ambient in S1 continuous duty at the rated input power. At high ratios and high input powers, the thermal rating may be the limiting factor rather than the mechanical torque rating.<\/p>\n

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Thermal Power Rating<\/div>\n

The thermal power rating (P-th) of each NMRV size and ratio is published in the Korea Ever-Power gearbox data sheet. P-th is the maximum continuous input power that keeps the housing below 80\u00b0C in a 40\u00b0C ambient environment with the standard natural convection aluminium housing and no added cooling. At 50\u00b0C ambient, derate by 10 to 15 percent. At 60\u00b0C ambient, derate by 20 to 25 percent or add a cooling fan kit to the gearbox.<\/p>\n<\/div>\n

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Intermittent Duty Uplift<\/div>\n

For intermittent duty applications (conveyor not running continuously; packaging machine with frequent starts and stops), the thermal rating can be increased above the S1 continuous rating. The Korea Ever-Power NMRV data sheet provides a duty factor correction table that allows the thermal input power rating to be increased by 15 to 40 percent for intermittent duty cycles with adequate rest periods for cooling between running periods.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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6. Gearmotor Combinations: NMRV Plus Three-Phase Motor<\/h2>\n
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Korea Ever-Power supplies the NMRV worm gear reducer matched and assembled with a Y2 series three-phase induction motor as a complete gearmotor unit. The motor\u2019s IEC B5 flange connects directly to the NMRV input flange \u2014 no coupling, no adapter plate, and no separate alignment procedure. The combined unit is delivered as a single bolt-down component ready for installation. These gearmotor assemblies are detailed in the gearmotor combination product section<\/a>.<\/p>\n

For applications requiring higher output torque than a single NMRV unit can provide, Korea Ever-Power supplies double-stage worm gearmotor units \u2014 two NMRV reducers in series, providing gear ratios from 100:1 to 7,500:1. At 7,500:1 ratio, a 4-pole motor at 1,450 rpm produces an output speed of approximately 0.19 rpm (one revolution every 5 minutes) \u2014 suitable for very slow drives such as solar trackers and tide-control gates.<\/p>\n<\/div>\n

\"Gearmotor<\/p>\n
Korea Ever-Power gearmotor \u2014 NMRV plus Y2 motor assembled as a bolt-down unit<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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7. Application Areas<\/h2>\n\n\n\n
\"Worm<\/p>\n
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Pumps, Fans and HVAC<\/div>\n

Cooling tower fan drives, circulation pump drives, and ventilation fan drives for HVAC systems use NMRV 050 to NMRV 090 worm gear reducers at 10:1 to 30:1 ratios. The compact right-angle output allows the motor to be positioned alongside rather than in-line with the driven shaft, reducing the length of the drive train and simplifying maintenance access. For centrifugal pump drives where VFD speed control is used, the NMRV gearbox provides the fixed ratio step-down while the VFD trims the speed over the operating range.<\/p>\n<\/div>\n<\/td>\n

\"Worm<\/p>\n
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Food Processing and Packaging<\/div>\n

Conveyor drives, mixer drives, filling machine drives, and labelling machine drives in food processing and packaging facilities use NMRV gearmotor units at ratios of 20:1 to 60:1. The self-locking property at 40:1 and above prevents conveyor runback on inclined lines when the motor stops. For food hygienic areas, the NMRV aluminium housing with IP65 protection and food-grade synthetic gear oil (H1 NSF listed) provides the washdown resistance required without the premium cost of a full stainless steel gearbox.<\/p>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

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Materials Handling<\/div>\n

Roller conveyor drives, pallet conveyor drives, and accumulation conveyor drives. NMRV 063 to NMRV 090 at 20:1 to 40:1 is the standard gearmotor specification for roller conveyor drives at 10 to 60 m\/min belt speed.<\/p>\n<\/div>\n

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Chemical and Pharmaceutical<\/div>\n

Mixing vessel agitators, reactor stirrer drives, and dosing pump drives. High-ratio NMRV at 40:1 to 100:1 with explosion-proof motor option for Zone 2 areas where the YB2 explosion-proof motor is paired with an NMRV gearbox.<\/p>\n<\/div>\n

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Agricultural Machinery<\/div>\n

Feed auger drives, manure spreader drives, and grain handling auger drives use NMRV 075 to NMRV 110 at 20:1 to 60:1 for the compact torque density and self-cleaning worm tooth geometry that handles abrasive or fibrous material ingress better than helical gears.<\/p>\n<\/div>\n

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Stage and Architectural<\/div>\n

Theatre fly loft drives, curtain track drives, and architectural shading system drives use NMRV gearmotors at 40:1 to 100:1. The self-locking property provides passive load holding at any position without a separate brake, critical for overhead loads above occupied areas.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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\"Korea<\/p>\n

CNC Worm Shaft Grinding<\/div>\n<\/div>\n
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\"Korea<\/p>\n

CE and ISO Certified<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Export Packaging<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Quality Inspection<\/div>\n<\/div>\n<\/div>\n

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8. Frequently Asked Questions<\/h2>\n
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How often should the oil in an NMRV worm gear reducer be changed?<\/div>\n<\/div>\n
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Korea Ever-Power NMRV series reducers are factory-filled with a viscosity-grade synthetic or mineral gear oil matched to the housing size and ratio. The first oil change is due after 500 to 1,000 operating hours (break-in period) to remove fine wear particles generated during initial running. Subsequent oil changes are due every 5,000 operating hours for mineral oil or every 10,000 hours for fully synthetic oil, or annually whichever comes first. For applications in high ambient temperature environments (above 40\u00b0C) or in clean-room areas where food-grade synthetic oil is specified, consult the Korea Ever-Power oil specification data sheet for the correct viscosity grade and change interval for your specific installation conditions.<\/p>\n<\/div>\n<\/div>\n

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Can a worm gear reducer be mounted in any orientation?<\/div>\n<\/div>\n
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The standard Korea Ever-Power NMRV reducer is designed for horizontal input shaft installation with the motor on the side (HW or HS mounting, where the motor flange is on the horizontal face of the gearbox housing). Other mounting orientations \u2014 motor-on-top (VF mounting), motor-on-bottom (VB mounting), or motor-at-right-angle configurations \u2014 are possible but require a change in the oil fill position and level to ensure the worm and worm wheel bearings remain lubricated in the non-standard orientation. Korea Ever-Power NMRV gearboxes have multiple fill, drain, and breather plug positions on the housing to accommodate all standard mounting orientations. Specify the required mounting orientation when ordering to receive the unit with the correct oil level marker and filled appropriately for the specified installation position.<\/p>\n<\/div>\n<\/div>\n

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When should a helical gear reducer be specified instead of a worm gear reducer?<\/div>\n<\/div>\n
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Specify a helical gear reducer (Korea Ever-Power R series inline helical or F series parallel shaft helical) instead of a worm gear reducer when: the application requires high efficiency above 93 to 96 percent (helical gears achieve this at all ratios; worm gears cannot above 20:1); the input power exceeds approximately 22 kW (the practical upper limit of standard NMRV worm reducers); the application requires very long continuous running at high load factors where worm gear heat generation would necessitate oversizing the gearbox unit; or the output shaft must be inline (parallel) with the motor shaft rather than at a right angle. Worm gear reducers are the preferred choice when right-angle output, self-locking, compact footprint, or simple single-stage high ratios are the primary requirements and efficiency is a secondary consideration.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Korea Ever-Power \u00b7 NMRV Worm Gear Reducers and Gearmotors<\/div>\n

Need a Worm Gear Reducer or Gearmotor for Your Application?<\/h2>\n

Korea Ever-Power NMRV series: sizes 025 through 150, ratios 5:1 to 100:1, matched and assembled with Y2 series motors as complete gearmotor units. In stock for fast delivery worldwide.<\/p>\n

View Worm Gear Reducers<\/a><\/p>\n<\/div>\n<\/div>\n

Edited by Cxm<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Korea Ever-Power \u00b7 RV \/ NMRV Series \u00b7 Worm Gear Reducer Guide What Is a Worm Gear Reducer? RV Series Application Guide A worm gear reducer converts the high speed, low torque output of a standard electric motor into low speed, high torque output through the action of a helical worm screw meshing with a […]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[28],"tags":[],"class_list":["post-174","post","type-post","status-publish","format-standard","hentry","category-industrial-electric-motor"],"_links":{"self":[{"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/posts\/174","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/comments?post=174"}],"version-history":[{"count":2,"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/posts\/174\/revisions"}],"predecessor-version":[{"id":177,"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/posts\/174\/revisions\/177"}],"wp:attachment":[{"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/media?parent=174"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/categories?post=174"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/fi\/wp-json\/wp\/v2\/tags?post=174"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}